I have never seen a DeVere enlarger but have had the same problem with my Beseler 4X5, especially as I have aged . I have managed this way which perhaps could be adapted tothe DeVere. The knob for focusing is made of plastic and held on to a shaft with a screw in the center. This knob is about 3" in diameter, and quite flat with knurling around the edge. I drilled four holes through the flat part and put in screws about 2" long with a nut hoding them in place. I then got some wooden pieces of a width such that they will go between the screws and act like a lever to turn the focusing knob. I've made up several of these of varying length (one could be 3 or 4 feet long) and drilled a hole or two to hold them on the focusing knob. They have worked really well for me after I wasted about $100 buying flex cables from Beseler which were absolutely, positively worthless. There is no spring - these could be mad of aluminium or just about anything.

I would be very interested to hear if this works for you as I have never seen anything like it. If it sounds useful I could try and send pictures (At present I don't have a digital camera and have no idea how to send, but I can probably scare up someone.